204 Dr. Wallace on 
follow within forty-eight hours after birth to be generally suc- 
cessful. 
Experiment, August 20th, one ? of the second brood emerged, 
after thirty-six days spent in cocoon; on the 2Ist, a second 2 came 
out in the evening after thirty-four days’ interval in cocoon; on 
the 23rd a ¢ emerged ; coition ensued that night with the second 
female. (I was afraid the first 2 might be stale, so to make sure 
I excluded her from the cylinder “aux mariages.”) The female 
separated the following night from the male and Jaid eggs to the 
number of 170; the following nights she laid 54, then 42, 27, 17 and 
8; the last two lots were composed of eggs smaller in size, making 
a total of 318 eggs. After she had left the male on the evening of 
the 24th, I placed the same male with the first female, which 
had been kept in a cool place to retard its development, but 
which had already begun to lay eggs, 38 in number; the same 
night coition ensued, and as no other imagos but these three 
were out, no mistake could possibly arise; the night after coition 
she laid 121 eggs, then 45, 7, 13, 14, in all 238 eggs; the eggs 
laid by her before coition neoved to be of course barren. I 
numbered these lots 1 and 2 and kept them distinct, having 
dated them, and I placed them on Ailanthus trees under precisely 
the same conditions; the larvae hatched out well and seemed to 
be vigorous, but I thought that the second lot were smaller and 
passed more slowly through their changes, and certainly fewer 
remained to be sent Geen from the nursery to the larger plan- 
tation, ViZ. 
Noo: 318 eges: of these, placed out of doors on the trees, 266 
hatched out Sept. 7th ; they passed through their Ist moult Sept. 
12th—15th, five days’ interval; they commenced their 2nd moult 
on Sept. 16th, four days’ interval; and of these 130 were sent 
down to the Ailanthery by the railway side on the 20th Sept. : on 
Oct. 5th they were passing through their last moult. 
No. 2. 172 larvee hatched out a 200 eggs; on Sept. 19th they 
commenced their 2nd moult, and, on the 20th, 67 only were left 
to go down to the railway. 
It is clear, therefore, that a male can if necessary be used twice 
for coition, but it is very probable that the resulting generation 
will be possessed of inferior vitality. 
During coition the males remain sometimes suspended in mid- 
air from the bodies of the females, sometimes clinging to their 
bodies. When the females require the male they call, or rather 
extrude their ovipositor and generative apparatus; the males 
fluttering near seem attracted by a sense unknown to us, and, 
